fix: Add .prettierrc.json to disable Prettier

Add a `.prettierrc.json` file containing a requirePragma rule to prevent
prettier changing all quotation marks to one type where both are used.
`.prettierignore` is only found if it is in the workspace root directory
which is incompatible with a multiroot workspace.

.prettierrc.json

@@ -0,0 +1,3 @@
+{
+  "requirePragma": true
+}